A psalm of David. Hashem said to my master, Sit at My right hand until I make your enemies a footstool for your feet: ... Hashem has sworn and will not relent: You are a priest forever because of the word of Malki Tzedek:
The question is asked – about whom was this said? The Gemara states (Nedarim 32b), Hakadosh Baruch Hu wanted to bring forth the Kehuna from Shem ben Noach, that his descendants would be the Kohanim. However, he then placed Avraham's blessing before the blessing of Hakadosh Baruch Hu – אֵל עֶלְיוֹן אַבְרָ ם לְאֵל עֶלְיוֹן קֹנֵה שׁ ָמַיִם וָאָרֶ ץ וּבָרוּך בָּרוּך.
Avraham said to him: “Does one place the blessing of a servant before the blessing of his Master?” Immediately Shem was punished, and Hakadosh Baruch Hu swore the Kehuna would be given to Avraham instead. The above Pesukim are said about Avraham Avinu; from here we see that Hakadosh Baruch Hu swore to Avraham that the Kehuna would be given to him, and this change is because of the words of Malki-Tzedek (Shem).
Rabbotai, why was it necessary to swear? And furthermore, why did Hakadosh Baruch Hu seat Avraham Avinu at His right hand? As is known, the war of the kings was a bloody war, therefore, Avraham Avinu shed blood – and if so, how can he be a Kohen?! The Shemen Rosh explains, this is why Hakadosh Baruch Hu said to him: "Sit at My right hand – you did not fight!" But what is it that Avraham did, if not fight? Chazal say (Bereishit Rabbah, 43:3) he would throw dust at them, and it would become swords; straw and it would become arrows. Additionally, they would throw swords at him, and they’d become dust; arrows would become straw. Hakadosh Baruch Hu said to Avraham Avinu: "Sit at My right hand – you throw sand and straw – you don't touch swords! I will take care of it – until I make your enemies a footstool for your feet – I will finish them off!"
It turns out that Avraham Avinu didn't kill anyone, rather the angels did everything. And therefore, Hakadosh Baruch Hu swore to him: "You are a Kohen forever" – because he had nothing to worry about, since he didn't kill anyone!
The Chatam Sofer explains that Hakadosh Baruch Hu told David HaMelech that he could not build the Beit Hamikdash because he had shed much blood, and Avraham Avinu also worried about this after shedding the blood of the four kings. Therefore, Avraham didn't build another altar until Hakadosh Baruch Hu commanded him to do so on Har HaMoriah. And what Malki-Tzedek told Avraham is that he remained a Kohen and was not disqualified by the war, because it was not him who carried out the killing directly.
This being so, the Shemen Rosh states, Avraham Avinu called the place of the Beit Hamikdash by the name הַ ר only after the Akeida, because beforehand there was the war of the four kings and Avraham worried that perhaps he had blood on his hands and consequently was disqualified. Hakadosh Baruch Hu told him: "Sit at My right hand – you didn't do anything, rather I did everything! – You are a priest forever" – and why did He promise him (swear) that he would be a Kohen? Since Hakadosh Baruch Hu sent him to the Akeida, and Chazal say that he was like a Kohen Gadol at the time of the Akeida – and a Kohen Gadol doesn't become impure for his seven relatives – therefore Hakadosh Baruch Hu told him: "You will be a Kohen and even though you will perform the Akeida you will not become impure!"
The question arises – Hakadosh Baruch Hu tells Avraham Avinu to throw sand, and arrows come out and everyone dies, and everything is perfectly fine – Avraham Avinu was not disqualified from the Kehuna. But didn't Hakadosh Baruch Hu tell David HaMelech to do the same? What's the difference?!
In the story of the Akeida, an angel comes from heaven and says: אַ בְ רָ הָ ם אַ בְ רָ הָ ם וַיֹאמֶ ר הִ נֵּנִי. Why did the angel call him 'Avraham' twice?
Hakadosh Baruch Hu told him: "Avraham, you have nothing to worry about. If I want someone to kill a soul yet still be able to be a Kohen and build the Mikdash, do you know what I do? I change his name! You fought the war of the four kings when you were called 'Avram' and you were uncircumcised. Now your name has been changed to 'Avraham' and you have also circumcised yourself, therefore you have nothing to worry about!"
But then suddenly, Hakadosh Baruch Hu calls out to him: וַיֹאמֶר אֵלָיו אַבְרָ הָם וַיֹאמֶר הִנֵּנִי. Avraham is told to take his son and sacrifice him, and he says to Hakadosh Baruch Hu, "But You already changed my name, so won't I now be disqualified from the Kehuna?!" Hakadosh Baruch Hu says to him, "You are a Kohen forever according to My word with Malki-Tzedek. Go and don't be afraid!" Avraham Avinu proceeds to go bind his son, and an angel comes down from heaven and shouts to him: אַ ל תִּ שׁ ְ לַח יָדְ ך אֶ ל הַ נַּעַ ר וְ אַ ל תַּ עַ שׂ לוֹ מְ אוּמָ ה – Do not stretch out your hand against the lad, and do not do anything to him... for now I know that you are G-d-fearing, and you have not withheld your son, your only one, from Me. He was tested and passed the trial, and therefore immediately the name of the place changes to ‘mountain’: הַר ה' יֵרָאֶה. This becomes the Beit Hamikdash!
